Safety papers have already been proposed, comprising chemical reagents to the oxidizing-reducing agents used in eradicator products, such as those marketed under the name of "CORECTOR" or "SLOAN'S". Such fluorescent papers generally develop, upon contact with these oxidizing-reducing products, a colouring which is often slight, hardly visible or invisible to the naked eye, but representing, on the other hand, an inconvenience for certain uses in which, in particular, the non-fluorescence of the paper is, on the contrary, desired, for example as monitoring means.
A paper containing chemical reagents to acids, to alkalis, to chlorinated bleaching reagents, to ink eradicators, is also known. Particular mention may be made of the teaching furnished by Patents FR 2 365 656, 2 399 505 and FR 2 402 739. Papers thus treated do not provide a suitably distinct coloured reaction.
Another proposition has also been made by Patent FR 2 580 303, providing the incorporation of iron(III) and a stabilizing agent giving a coloured complex with iron(II). The recommended method is delicate to carry out, involves products of high cost and leads to a paper which initially presents a background colouring which, moreover, tends to accentuate with age. A paper according to such a proposition presents, in addition, a reactivity limited to the pair of oxidizing-reducing agents, which reduces its forgery-proof characteristics.
The present invention aims at proposing a novel safety paper which responds better than heretofore to the different requirements of a forgery-proof safety paper and which may easily be manufactured in accordance with traditional methods and at an advantageous cost price.
It is an object of the invention to provide a forgery-proof safety paper not presenting any noteworthy residual colouring, nor fluorescence, capable of reacting to chemical reducing agents, to the pair of oxidizing-reducing agents, as well as to the eradicator felts, with a sufficiently high sensitivity to satisfy the relevant harsh tests.
It is another object of the invention to provide a forgery-proof safety paper presenting, after treatment, a clear white colouring not undergoing substantial alteration in the usual storage time at the consumer's.
It is a further object of the invention to propose a forgery-proof safety paper whose sensitivity of reaction to the pair of oxidizing-reducing agents is improved.